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Home , Alkanna, Boraginaceae, Heliotropium, Heliotropium arborescens, Nonea

On the Occurrence of Exudate Flavonoids in the Family () Eckhard Wollenwebera*, Rüdiger Wehdea, Marion Dörra and Jan F. Stevensb a Institut für Botanik der Technischen Universität, Schnittspahnstrasse 3, D-64287 Darmstadt, Germany. Fax: 06151/164630. E-mail: [email protected] b Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA; Present address: Leibniz Institut für Pflanzenbiochemie, Weinberg 3, D-06120 Halle/Saale, Germany * Author for correspondance and reprint requests Z. Naturforsch. 57c, 445Ð448 (2002); received February 8, 2002 , , Tricetin Methyl Ethers Externally accumulated flavonoid aglycones have been found for the first time in Nonea . They exhibit only flavones, one of thembeing the rare tricetin-4 Ј-methyl ether. Within the subfamily , exudate flavonoids appear to be a rare character.

Introduction collected in Chile, near La Serena, Prov. De Elqui (P. Lo´ pez 2471). In each case, concentrated solu- Reports on the occurrence of flavonoid agly- tions were defatted (MeOH, Ð10∞, centrifugation) cones in Boraginaceae are scarce so far. In the and passed over Sephadex LH-20, eluted with scope of ongoing research on the distribution of MeOH, to separate the flavonoids fromthe terpe- flavonoid aglycones on surfaces we have now noids. The flavonoid portions of N. lueta were fur- studied some members of this family. We found ther chromatographed over polyamide DC-11, exudate flavonoids in three European Nonea spe- eluted with toluene and increasing quantities of cies and in two Heliotropium species fromChile. methylethyl ketone and methanol. Fractions were Several indigeneous species of the subfamily Bora- monitored and comparisons with markers were ginoideae were found devoid of exudate flavo- done by TLC on polyamide (DC 11, Macherey- noids. Ð Nagel) with the solvents a) petrol100Ð140 tolu- eneÐMeCOEtÐMeOH 12:6:1:1 v/v/v/v, b) tolu- Material and Methods Ð Ð Ð ene petrol100Ð140 MeCOEt MeOH 12:6:2:1 v/v/ Nonea lutea Bory & Chaub. and N. rosea Link v/v, and c) tolueneÐMeCOEtÐMeOH 12:5:3 v/v/v, were cultivated in the Botanical Garden of the and on silica with solvent d) tolueneÐMeCOEt 9:1 University of Darmstadt. Aerial parts were col- v/v. Chromatograms were viewed under UV lected in bulk fromflowering ( N. lutea: May, (366 nm) before and after spraying with “Natur- 1999; N. rosea: July 2000, August 2001. Vouchers: stoffreagenz A” (1% of diphenyl-boric acid-etha- Botanischer Garten der TU Darmstadt). Fresh nolamine complex in MeOH). Authentic samples material was briefly rinsed with acetone to dis- of flavonoids were available in E. W.’s lab. Ð At- solve the lipophilic material accumulated on leaf mospheric pressure chemical ionization (APCI) and stemsurfaces. Someplants of N. pulla (L.) mass spectra were recorded on a PE Sciex API III DC. were collected at natural sites near the Kyff- Plus triple-quadrupole instrument. NMR spectro- häuser (Germany; coll. H. Dietrich, July 1999; scopy was run on a Bruker DRX 600 instrument 1 voucher at HAL) and in N-Burgenland (Hackels- at 600 MHz ( H) in DMSO-d6. berg, Lake Neusiedl, Austria; coll. K. Vetschera, Compound 1 was isolated from some combined June 2001; voucher at WU), respectively. The air- fractions of N. lutea by prep. TLC on silica with dried samples were also briefly rinsed with ace- solvent e) tolueneÐdioxaneÐHOAc 18:5:1 v/v/v. It tone. Aerial parts of Heliotropium pycnophyllum was further purified by HPLC on a 10 µmEconosil Phil. were collected in Quebrada Botija (24∞31ЈS, RP-18 column (250 ¥ 10 mm) using a linear gradi- 70∞33ЈW.), Prov. Antofagasta, Chile (Dillon 5355). ent from40% to 100% MeCN in 1% aq. HCOOH Heliotropium stenophyllum Hook et Arn. was also over 30 min at 5.6 ml/min. The peak fraction con-

0939Ð5075/2002/0500Ð0445 $ 06.00 ” 2002 Verlag der Zeitschrift für Naturforschung, Tübingen · www.znaturforsch.com· D 446 E. Wollenweber et al. · Flavonoid Aglycones in Boraginaceae taining compound 1 was collected and taken to sible when the hydroxy group at C-4Ј carries the dryness by rota-evaporation and lyophilization. Its methyl substituent. Compound 1 was therefore melting point is reported here for the first time: identified as 5,7,3Ј,4Ј,5Ј-pentahydroxyflavone-4Ј- ∞ λ 274 C (dec.). UV (MeOH) max 331 and 268 nm; O-methyl ether. +NaOH: 373, 316 and 274 nm; +AlCl3: 346, 301 Samples of eight further species of Boragina- and 277 nm, unchanged on addition of HCl (Lit. ceae were collected in the field around Darmstadt (Ulubelen et al., 1984): MeOH (331 nm), +NaOH or in the Botanical Garden of the University of (373 nm)). The 1H spectrumshowed three pheno- Darmstadt: azurea Mill., A. sempervirens δ lic OH signals ( H 12. 87 (OH-5), 10.92 and 9.57), L., officinalis L., minor L., Cyno- δ two equivalent B-ring protons ( H 6.96, s, 2H, glossum officinale L., vulgare L., Ј Ј δ H-2 and H-6 ), a singlet at H 6.61 typical of a arvensis (L.) Hill, and officinale L. flavone H-3, two meta-coupled A-ring protons They were also rinsed with acetone and the con- δ ( H 6.42 and 6.20, J = 1.8 Hz, H-8 and H-6), and centrated solutions were checked for flavonoid δ Ј one OMe singlet ( H 3.76, 4 -OMe). Fromthe MS aglycones by TLC. (MH+, m/z 317) and 1H spectrumit was deduced that compound 1 was a 5,7,3Ј,4Ј,5Ј-pentahy- Results and Discussion droxyflavone monomethyl ether. The O-methyl group was placed at position 4Ј for two reasons, Nonea lutea, Nonea pulla, and N. rosea were (1) the A-ring proton resonances were not shifted found to exhibit exclusively flavones (Table I). downfield compared to 5,7-dihydroxy flavones Some of these are rather rare natural products. (Markhamand Geiger, 1994; 7-O-methylation Tricetin-4Ј-methyl ether was reported only once causes a downfield shift of the H-6 and H-8 before as an aglycone, namely from the leaf of doublets by about 0.2Ð0.4 ppm), and (2) the B- Passiflora palmeri (Ulubelen, 1984.). Tricetin- ring H-2Ј and H-6Ј protons gave rise to a 2H sin- 3Ј,4Ј-dimethyl ether (apometzgerin) was known glet indicating B-ring symmetry which is only pos- fromthe grass Poa hueca (Rofi and Pomilio, 1985 E. Wollenweber et al. · Flavonoid Aglycones in Boraginaceae 447

Table I. Flavonoid patterns of 3 Nonea species. Table II. Flavonoid patterns of 2 Heliotropium species.

Flavones N. lutea N. pulla N. rosea Flavonoids H. pycno- H. steno- H. stenoph. Ð phyllum phyllum Lit.* Apigenin x x (x) Ap-7-Methyl ether x x x Chrysin x Luteolin x (x) Chrys-7-Me x Lut-7-Me x x Luteolin-7-Me x Lut-3Ј-Me (x) Galangin x x Lut-4Ј-Me (x) Gal-3-Me x x x Lut-7,3Ј-diMe x (x) Gal-7-Me x Lut-7,3Ј,4Ј-triMe x Gal-3,7-diMe x Tricetin-4Ј-Me x x Kaempferol x Tric-3Ј,4Ј-diMe x Kae-3-Me x Tric-3Ј,4Ј,5Ј-triMe x Kae-7-Me x Kae-3,7-diMe x Kae-7,4Ј-diMe (x) Kae-3,7,4Ј-triMe x Quercetin x [and as a C-glycoside fromthe liverwort Apo- Qu-3-Me x metzgeria pubescens (Theodor et al., 1980)]. Tri- Qu-7-Me x cetin-3Ј,4Ј,5Ј-triMe had so far been reported only Qu-3,7-diMe (x) x Ј as a constituent of 4 Gramineae (Kaneta and Sugi- Qu-3,3 -diMe (x) x Qu-5,3Ј-diMe x yama, 1973). Recently it was also encountered on Qu-3,7Ј-diMe x aerial parts of a Scrophulariaceae (Wollenweber, Qu-3,7,4Ј-triMe x unpubl.). Nonea appears to be the first in Pinocembrin x x Naringenin (x) x which these tricetin derivatives are accumulated Nar-7-Me x x externally. Nar-7-Me-4Ј-Ac (x) The exudate of Heliotropium pycnophyllum Nar-7,4Ј-diMe x contains flavones and flavonols, whereas the exu- Eriodictyol x Eriod-7-Me x date of H. stenophyllum contains flavonols and fla- vanones (Table II). The flavonoid pattern exhib- * Urzua et al., 2000. ited by our material of H. stenophyllum is rather different fromwhat has been reported in literature previously. Neither did we see any trace of luteo- officinale, Cerinthe minor, Echium lin-7-methyl ether, nor was there any hint to the vulgare, , and Symphytum offici- presence of a 5-methoxy flavonol (which would nale were found devoid of flavonoids. appear as a brilliant yellow fluorescent spot on tlc In the subfamily , there is only one in UV light). In both studies, aerial parts were col- report so far: verbenacea was found to ex- lected during the flowering period and dipped in hibit three highly methoxylated flavonols (Van de dichloromethane or rinsed with acetone, respec- Velde et al., 1982; Lins et al., 1990). tively. The different flavonoid patterns observed In the subfamily , seven species might, therefore, point to the existence of varieties of Heliotropium were reported previously to ex- or of chemotypes in this species. hibit exudate flavonoids (Urzua et al., 2000). They This is only the second time that exudate flavo- produce several flavanones and dihydroflavonols noids have been found in members of the subfam- (including natural acetates), two flavones, and a ily Boraginoideae. The first report was on flavo- series of flavonols. H. megalanthum is outstanding nols fromaerial parts of orientalis (El in producing a flavonol and two flavanones with Sohly et al., 1997). It is striking that in Nonea ex- the relatively rare 3Ј,4Ј,5Ј-triO-substitution. We clusively flavones have been detected, whereas Al- were unable to detect any flavonoid aglycones in kanna exhibits 6 flavonols and lacks flavones. (Botanical Garden, Eight further species belonging to this subfamily Darmstadt), so flavonoid excretion obviously is have also been checked for the presence of exu- not a general character of the genus. date flavonoids. The acetone leaf rinses of An- In a recent study on the leaf surface in Boragi- chusa azurea, A. sempervirens, Borago officinale, neae, Nonea lutea, N. pulla, N. caspica and other 448 E. Wollenweber et al. · Flavonoid Aglycones in Boraginaceae taxa were reported to bear long glandular hairs, and that many more species need to be checked consisting of three or more stalk cells and an elon- in the future before any chemosystematic conclu- gated secretory cell (Selvi and Bigazzi, 2001). sions can be drawn. Urzua and co-workers (2000) pointed out that, in Heliotropium, the presence of glandular trichomes Acknowledgements. is not necessarily a prerequisite for the presence The authors want to thank Dr. Walter Welß (In- of exudate flavonoids, but is correlated with the stitut für Botanik und Pharmazeutische Biologie, amount of resin produced. For two varieties of Abt. Geobotanik, der Universität Erlangen) for H. chenopoidiaceum, on the other hand, they ob- seed of N. rosea, and Drs Helga Dietrich (Biolo- served that the presence/absence of glandular gisch-Pharmazeutische Fakultät der Universität trichomes had no influence on the flavonoid pat- Jena) and Karin Valant-Vetschera (Institut für Bo- terns observed in both varieties (Urzua et al., tanik der Universität Wien) for some dried plants 1998). of N. pulla. Thanks are also due to Dr. Michael O. The genus Nonea comprises 35 Mediterranean Dillon (Botany Department, The Field Museum, species, Heliotropium comprises some 250 species, Chicago, IL) for herbariummaterialof Heliotro- occurring in the tropic and temperate zones. In to- pium pycnophyllum and to P. Lo´ pez, Sepulveda tal, the borage family houses some 2000 species in (Concepcio´ n Chile), for collecting H. stenophyl- 100 genera (Willis, 1973). It is thus obvious that lum. E. W. wishes to thank the Deutsche For- the results presented here are not representative schungsgemeinschaft for financial support.

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